Torque tool and release mechanism



March 1957 V E. D. ETHINGTON ET AL 2,786,378

TORQUE TOOL. AND RELEASE MECHANISM 2 Sheets-Sheet 1 Filed Aug. 51. 1954 m m 6 4 a n m w v 3 m E 1 1 a a V v mw w Wm Q d S -mm w H m\ S. 3 8 a S March 26, 1957 Filed Aug. 31, 1954 E. D. ETHINGTON ET AL TORQUE TOOL AND RELEASE MECHANISM INVENTORS flame 4 TORQUE TOOL AND EASE MEGHAN'ISM' Edward D. Ethington, CedarFalls, andPaui Ethington, Cedar Rapids, Iowa Application August 31, 1954, Serial No. 453,389 is lates- (9 in- 2A) This invention relates to torque applying tools and to force release mechanisms ijor such tools and for general application. More particularly, .in one aspect, the invention is app ic ble o a t rque pp y n tool f n i n to an operator when a predetermined value of torque is applied. In another aspect, the invention relates to jin ce release mechanisms especially suited to torque measuringtools although the invention is not limited thereto in it u u nes Th rq tool as num o s app c t ns in der indus y i i the la o ry n a sem ly, an in h hop- A K105i common ppli a io fo ex mp i the tig tening of a screw threaded fastener to a given value of torque to produce a desired tension in the shank of the fastener.

Torque wrenches known in the prior art take a variety 9 e ms nd s l a l ssifiabl ge r ly ith r a .thefrigid lever arm type or the flexible lever arm type. Here tofore, so far as known, it has been the practice to construct both types of torque wrench as an integral bination of driving head, lever arm, and measuring mechanism. In this arrangement the torque lever arm is fixed and the associated measuring mechanism is designed and calibrated for the fixed lever arm length usually for oper ation over a single range of torque values. It is a common practice to use various accessories with either type of wrench. Such accessories serve as extensions from the driving head or extensions from the handle portion to permit access to the workpiece or to increase the effective lever arm of the tool. The prior art devices under such conditions require that a correction factor be applied to the measured value of torque to account for disturbance in the initial calibration occasioned by use of the accessory. This, of course, results in inconvenience and inefficiency in the use of the tool;

Both types of torque wrenches and tools, the rigid lever arm and the flexible lever arm known heretofore incorporate some form of elastic or spring member for measurement of the applied torque. The relationship between .spr ing deformation and applied force throughout the range of force must be known in order to produce accurate measurement. This relationshi expressed as the rate of change of force with respect to displacement or spring rate must be known for each tool. So long as torque measurement depends upon spring rate, a high degree of a cu a y a e obt ned on y by ind idu l ca ibration of the tools because of the lack of uniformity of spring rate in otherwise identical springs. This requirement in prcsent practice niilitates against advantageous volume production techniques and leads to high .cost of torque me uring ls- It is the purpose of this invention to overcome these other disadvantages of the prior art devices. momenta of this..iuveut qn* to pr vid a att ne'njt for torque applying-tools which will indicate di- .,rectly in units of tocque the value of torque .ap l at a Kais r resa dlcss o th e e a m length of th .Uuit d States Patent '0 Another object is to provide .a torque applying tool in which thetorque setting may-be established-asa'function of .two independent variable quantities.

Another object is to provide a variable .force release mechanism which will yield at a predetermined :force value independently of the spring rate of-the mechanism.

A further object is to provide a torque applying tool having an improved force release mechanism which-produces a tactual and audible signal to the operator when a predetermined value of torque is applied.

it is an additional object to provide a variable force release mechanism in which the release force varies linearly with respect to shaft rotation.

A further object is to provide a torque wrench with a releasable coupling which automatically resets after each operation.

These and other objects and the advantages of this invention will become apparent from the, descriptionwhich follows in view of the accompanying drawings, in which:

Figure l is an elevational view of an illustrative embodiment of the invention as an attachment to a conventional wrench.

Figure 2 is a schematic representation of the assembly shown in Figure l for explanatory purposes.

Figure 3 is a s mat o ce di ram to aid n th description of the force release mechanism.

Figure 4 is a sectional view of gne embodiment of the invention.

Figure 4a is a sectional view of the embodiment of Figure 4 with the parts in a different position.

Figure 5 is an elevation view in section Qf 3 m n?! embodiment of the invention.

Figure 5a is a sectional view of the embodiment of Figure 5 with the parts in a dififerent position.

Figure 6 is a plan view in partial section of the embodiment shown in Figure 5.

Figure 7 is a plan view of one element of the force release mechanism of the embodiment shown in Figures.

Figure 8 is a perspective view of a modification of one of the parts.

The invention comprises a driving member and a driven member, the members being .pivotable or rotatable engagement at one point and connected through a releasable coupling at another point. The driven member is connect'able to torque applying tools which may have dilf erem lengths f lever ms- Th release f rc f t e pling is adjustable in accordance withtwo factors; the value of torque to be applied and the length of the lever arm. An indicator is provided which reads directly in terms of applied torque regardless of the nature or length of the tool. V

The force release mechanism comprises two force transmitting elements one of which has a variable slope surface and the other of which has an engaging portion. The elements are relatively movable for the. selection of the point of engagement at the desired slope. One element is yieldably urged by an elastic force or spring into engagement with the other. The release force of the mechanism is independent of spring rate and release .99- curs instantaneously.

Referring now to the drawings the various illustrative embodiments of the invention will be described in detail. Throughout the drawings like parts are designated by like reference numerals.

Figure 1 shows a torque applying tool '10 of a conventional type fitted with the inventive attachment through an adaptor 20. The tool 10 comprises a drive head 11 provided with a drive square 12 for engaging the socket of a work engaging fitting (not shown) of any suitable kind- Connected with. the .driye head 11. is a ever ar 3 w i h ay s i a be si s at and of any appropriate length. The end portion of the lever arm 13 which would normally be the handle portion extends into an axial bore in the adaptor 20. The adaptor bore is of such size as to accommodate the handle of the tool being used and the two members are preferably detachably secured together by any suitable means such as one or more'set screws. As will appear more fully hereinafter the lever arm 13 and the adaptor 28 may, for'certain applications of the invention, be made as a single integral part.

In the embodiment of Figure 1 the adaptor is secured to a driven member 3b which in turn is connected to a driving member 50. The driving member includes an outer sleeve 51 preferably cylindrical and of suitable length to accommodate the hand of an operator. The outer surface of driving member 5% constitutes a grip portion adapted to receive a manually exerted force. The sleeve is provided with a flat or any other desired surface 52. for bearing scale divisions which may be calibrated in units of torque such as foot-pounds or inchounces. A pointer or index mark 8% is mounted on a rotatable shaft 60 for movement over the scale to select the desired value of torque. The driving member 59 also includes an end cap 70 secured to the sleeve by screw thread engagement.

The driving member encases the driven member 3% and is in pivotal engagement therewith through the pivot pin 53 adjacent one end of the driving member. The driving member also houses a releasable coupling, to be described subsequently, which is interposed between the driving and driven members adjacent the other end 'of the driving member.

Referring now to Figure 2, there is shown a schematic line diagram to aid in explaining the force system in the illustrative embodiment of Figure 1 and the embodiments to be described subsequently. The parts corresponding to those of Figure l are designated by the same reference numerals.

A manual force F is applied to driving member 59 by the hand of the operator and is shown as a concentrated force. The assumption of a concentrated force is made to simplify the explanation although it will be well understood that the operators hand applies a distributed force and the center of pressure may vary somewhat depending upon the configuration of the grip portion and the manner of gripping.

The torque tool has a lever arm length l which for a given wrench is fixed but varies among different Wrenches. From the point of connection between the lever arm and adaptor, the force F is displaced a distance 12. At the pivotal connection between the driving and driven memher a portion of the force F is transmitted to the driven element and is represented as a reaction force R. The releasable coupling is represented schematically by two elements, one element having a surface of variable slope and an engaging element 56. A portion of the force F is transmitted to the driven member through the releasable coupling and is represented as the reaction force R. The point of force F is displaced a distance d. from the force R and a distance d. from the force R.

The well known expression for torque which yields the value of torque applied to the workpiece is:

T=FL

an effective length By inspection it is seen that L In turn this force is transmitted where F is the force applied through a lever arm having 1' is the sum of l and b and the general expression above becomes: T=F(l+b) (2) The value of F can be expressed in terms of the reaction forces R and R as follows:

Equation 4 shows that the torque applied is a direct function of the lever arm length and the reaction force R on the releasable coupling. Thus, the applied torque can be controlled by controlling the value of R. Rearranging Equation 4;

shows that the value of R must be set in accordance with the desired value of torque T to be applied and the length of the eliective lever arm l+b. It thus becomes apparent that a desired value of torque may be applied with a wrench lever arm of any length if the force R is predetermined in accordance with two factors, lever arm length and desired torque. This is accomplished by the provision of a coupling which will release at the predetermined value'to interrupt the applied torque. -There fore, the release force of the coupling must be set in. accordance with the two factors mentioned above.

The inventive coupling admirably suited to this re quirement is disclosed in Figures 4, 5 and 7. The considerations in the operation of this coupling will be explained with reference to Figure 3. Consider the spherical element 55 acted upon by the force system shown. Force R represents the reaction force of the support for the ball 55 and the perpendicular force S represents a force applied by a yieldable element such as a spring. The force W is applied through a force transmitting element 56. When the force W has a component which just slightly exceeds and is opposite to force S, the spring element will yield permitting minute displacement of the ball 55. This relation obtains when W cos u=S At this condition, the value of R is:

R'=S tan a (7) From these considerations it now becomes apparent from Equations 5 and 7 that the torque transmitted to the workpiece is:

T= %3 )(l+b)S tan 0: s

For any given tool the values of d d 1 and b are constant. The first two factors of Equation 8 may be combined into a single constant value k. Equation 8 becomes:

T=kS tan 0!. (9)

embodiment of the inventive device is indicated by the following tabular presentation.

Note that the spring force S is constant for a given value of lever arm length l; data is. based u on "the fcllowing parameters: di= a and. 12:3 inches- Consider again the spherical element acted .upongby the forces shown in Figure 3. The surface of the element in the plane of the force W may be Characterized as having avariable slope as distinguishedfrom a constant slope. For the spherical surface, the slope is equal to the tangent of the angle a and increases from zero value when a is 90 degrees to an infinite value when a is zero degrees. The slope of the surface of the element at the point of application of force W increases continuously as the point of application moves downwardly as shown in Figure 3. it will be appreciated that many surface configurations other than spherical have a variable slope and that the spherical element is given merely as an example.

With the application of force W at a point or in a limited area on the surface of the element 55, the minute displacement of the element 55 permitted byyielding of the spring which applies force S causes the pointofapplicat-ion of-torce W to move downwardly a small amount. At this new position the slope of the surface is greater and the component of force W which is ,oppositeforce S increases. This causes further yielding of the spring without any increasein theforce Thus, the force F continues to move to a point of greater slope and the action is cumulative resulting in the instantaneous snap action of displacing the element 55 against the yielding spring until the force W' no longer has a 'component'directed oppositely to reaction force R. Instantaneous release of the coupling is thuslrealized.

It is especially noteworthy that the vrelease 'force of'the coupling is independent of the spring rate. "Thedisplacement of the element 55 occurs at the instant the :forceW has a component equal and opposite to the spring force '8. This spring force S may he applieda springhav'ing any rate or relation between force and'displacernentfland n s a h t l value f s in force, 'nq ths s r n rate, that determines at what value ofIforceW thecoupling will release. This is subject toone limitation in that the rate of change of spring force 5. with respectto displacement of element 5rnu st not jexceedth e rate of change of force due to the slope of the surface with re- .spect tov the displacement of element This condition is readily satisfied in practice.

The manner in which the foregoing prinq glfih g re apl d. in the a tu l m me s o h nt on is set forth in Figu es 5, 6 n 1 Referring to Figure 4 the adaptor which supports the d ive member 33 i sni ahly a y in c sle el .riece he the le er rm of a a one sn "I arm i se ured in plan by a set s rew At it oth end, the adaptor hasa reduced portion 3 1 andga threaded shank 5.2- T e thre ed s i .fi3'whi chfis prefer bly @51 H the .adaptqr- .....Jiven mem er-331s .Pr annu ar sh ulder 34.

. C'oad wi h t e. driven. member-133 is. .d ring membe sl'with 1 Adjacent thecther a .membs he sleev ssptcrideld with a th eaded p e on 53 ,h ch e gages the threaded sleeve portion of cylindrical and cap 70'.

. its: engine The end of the sleeve 5 1" abuts,a detent element pr 46'whi h s s a d a a h end f h... 31 provide a positive stop which assures that the sleeve cap have the same relative position each time {the deyice is assembled.

The shoulder 34 together with the engag g port'on of sleeve. 5 cons tu e a Pi t on ec on the We' n the d v n and driven m e s- Th flange 5' imits th axial motion of the sleeve 51 in one directio b en ment with the shoulder 34. It is noted th pivotal m n o s eev 5 wit sp c t d iv n numbe 33 ma occur in any plans n e the member areqyl n ricaL' p se betwe n h r ving m mber .5 01 e member 33 to estrain p o al mo ion un il a predetermined f fr' ,is pplie is a releasabl Q yi ldable coupling- The coupling comprises a detentelem 'nt'or 46 of any' suita le r ss-sectional config ratle etc a circular or rectangular. The insert. is supported .ey cap 7.0 in arecess havinga wall 72 withfafit close to prevent relative movement of the parts yet ermitting the insert tobe readily removed. i

The insert .46 constitutes a force transmitting element and defines on one of its axial faces a circular reee one diameterhaving a peripheral edge 47. On the. opposite ,face is a recess .of a different diameter having a pc- .ripheral edge 49. The recesses are axially aligned the center line of the driven member 33. Note that the circular recess of larger diameter has its peripheral edge extending to the face of the insert, whereas the smaller recess having edge 47 is counterbored a certain amount leaving annular shoulder 48. The reason for this construction will appear hereinafter.

Another force transmitting element having a variable slope surface .is shown as a spherical member or ball 55. .The ball 55 is upported in a a a b 3 a n. yield ingly urged into the recess in the insert 46 --by a resilient member shown as a coil spring 37. The spring .is seated against plunger 38 WhiCh'lS suitably limited .in its axial motion by a shoulder on the wall of bore 36. A set screw 39 engages one end of piston 38 and is accessible from the shouldered end of driven member 33., with the adaptor removed, to adjustthe force exerted by the spring on the h ll.

The ball is urged into engagement with the peripheral edge 47 of the aligned recess and the, point of engagement bet-w en e pe pher g and the variabl sl pe surface of the ball depends upon the diameter of the ;ree es s. {The hall 55 has a reference position within the bore such that itscenter is slightly inside or in alignment with {the axial fa of th r v n b rv Th the ball i onstrained against motion transversely of the driven member 33. The counterbore 48 is of such depth that the edge 47 of {the recess just engages, but does not displace the :ball from its reference position wh n the end cap -7- 0' is screwed into seating engagement-with sleeve 51.

The deten-t element 46 is removable from the recess 12 in the end ap an may e replaced n nnnthsr Pnsi i n or orientation in the recess 72. By rotating the detent clement through 1.80 degrees the larger recess defined by peripheral edge 49 is presented to the surface of ball .55. The axial length of the detent element including the sh u d 4.8 is su h h t th Pe ph r l e g 4 ins engages-the ball surface without displacing the ball from its :ret rence posi on A et of in r h v ng re e ses o d fli r nt diametersm y b p i The detent element 46 in the illustrative embodiment is constructed with only two recesses of different diameters an only tw faces f ,d t n e n ar and. It i l now be apparent that the detent element may be constructed with different configurations such as a cube 46' as sh wn in Figh1ie:8 .with each f i s si fe e p ed with rece f difierent diameters. This will pro td fieren t nns or or en ations Qfthe .deten't Q. a he h ll surface a a o respnntiihh *It'will be understood that t e ace of differetit positions'.

"curs, providing a tactual signal to the operator.

pivotal motion is limited by impact with the driven memwith the largest diameter recess 49' need not be counterbored but that the remaining faces with smaller recesses 747' and-47 should be counterbored to-such depth that change of position .of the detent element does not move the ball from the reference position. This prevents any disturbance of the spring force set by the position of the adjusting screw.

In operation of the embodiment of the invention of Figure 4 the detent element 46 is first positioned to providethe desired point of engagement between the surface of ball 55 and the peripheral edge of the recess in the detent element. This setting may be made in accordance with torque value desired to be transmitted by the tool. The spring force may then be adjusted by screw 39. This setting may be made in accordance with the effective lever arm length. Thus, first and second means are provided for predetermining the value of force on the driving member 50 at which the coupling will release. Obviously either means may be set in accordance with torque while the other means is then set in accordance with lever arm length. With a manually exerted force applied to the driving member forces will be transmitted to the driven l member through the pivotal engagement and through the coupling. When the predetermined value of torque is reached the spring will yield slightly and the engaging portion of the detent element will encounter an ever increasing slope on the variable slope surface of the ball. Instantaneous pivotal motion of the driving member oc- The ber providing an audible signal. The relative position of the parts in this condition is shown in Figure 4a. The motion is of such limited extent that the ball never completely leaves the recess on the detent element or, stated otherwise, the motion in the vicinity of the coupling engagement is less than the radius of the ball. Once the operator releases the force'on the displaced driving member, the camrning action of the ball under the influence of the springresets the driving member for another operation.

The embodiment of the invention illustrated in Figures 5, 6, and 7 is, in many respects, similar to that of Figure 4. The adaptor 20 is provided with an internal shoulder 22 which serves to positively seat the tool lever arm. The driven member 30 is secured to the adaptor by screw thread engagement. Driving member 50 comprises a sleeve 51 pivotally connected at one end to the driven member 30 by aligned pivot pins 53. The pivot pins should have a close fit to prevent play in the pivotal connection. Washers 57 of suitable material such as fibre or plastic maintain the spacing between the members. The pivot pins permit pivotal motion of the driving member 50 about a single transverse axis.

The sleeve 51 is provided with a flat 52 and axially extending slots 54 in diametrically opposite portions of the sleeve wall. The end cap 70 is screw threaded onto sleeve 51.

A releasable coupling is interposed between the driving and driven members adjacent the end cap. The coupling comprises a detent element 63 having a shaft portion 69 rotatably journalled in the slots in the driving member.

The shaft axis is perpendicular in direction to the axis of pins 53 and is fixed in position relative to the driven member 30 by locking engagement between the end cap and the end of the slots 54. The shaft at one of its ends carries an indicator arm 80 movable over the scale divisions on the surface of the fiat 512. The scale may be suitably calibrated in units of torque.

As seen in Figures and 7 the detent element is provided'with a groove 64 which is circular in cross section 'and which extends icircumferentially of the shaft axis.

The depth of the groove varies continuously from a minimumvah e to a maximum value over anangular range of180 degrees.) As shown in Fig. 7, the root 61 of the Ygtoove concentric with the shaft and the peripheral edge the groove on center and then olfsetting the stock on the lathe centers a desired amount to turn the outer surface eccentrically.

The force transmitting element having a variable slope surface and shown as ball is positioned in the axial bore 36 in driven member 39. Spring 37, seated against plunger 38 which is adjustably positioned by screw 39, urges ball 55 into mating engagement with the detent element. Since the root of the groove is concentric with the shaft the ball remains in its reference position for all rotative positions of the shaft. For this reason the spring force is determined only by the position of the adjusting screw.

The operation of this embodiment is similar to that of .the embodiment shown in Figure 4 but a continuous variation in the torque is available.

The shaft may be positioned in accordance with the value of torque desired to be applied and the spring force is then set in -accordance with lever arm length. The force applied to the driving member is transmitted through. the pivot pins and the releasable coupling. When the predetermined torque value is applied the coupling releases, producing a tactual and audible signal to the operator. The relative position of the parts in this condition is shown in Figure 5a. The driving member is automatically reset by operation of the spring and ball against the peripheral edge of the groove.

In this embodiment care should be taken to attach the adaptor to the tool such that the axis of shaft lies in the plane of rotation of the workpiece to be engaged by the tool. Any lateral thrust applied by the operator will be ineffective to change the torque applied to the workpiece and will be likewise ineffective to release the coupling. Thus, greater accuracy is obtained.

Referring again to Figure 7 it will be seen that if the peripheral edge of the groove is tangent at a point to the root of the groove, the release force will be zero for one position of the detent element. If the maximum depth of the groove is equal to or slightly less than the ball radius, the coupling will be substantially rigid or non-releasable for one position of the detent element. It has been found that the concentric root and eccentric periphery of the groove yields a substantially linear relationship between release force (and therefore applied torque) and the angular displacement of the shaft. The advantages obtained in calibration are obvious.

The detent element and the ball are preferably made of hardened and polished steel or other metal to minimize surface indentation and friction.

This invention has been described with respect to particular embodiments but such embodiments are illustrative only and are not to be construed as limitations. Many modifications will now occur to those skilled in the art. For a definition of the invention, reference is made to the appended claims.

We claim:

1. A torque tool comprising a driving member and driven member interconnected by a releasable coupling, and first and second independently adjustable means on said members for varying the force required to release said coupling each of said means exerting constant influence on the coupling release force throughout adjustment of the'other of said means.

2. A torque tool comprising a driving member and. a

anv angularly directed -forcezhaving a component-idsaid direction is" transmitted between the elements, means for adjusting the resisting means-to-vary-the magnitude of resistance, and means for adjusting said elements to select theslope of said surface, independently ofsaid-magnitude of resistance, at which'said elements are engaged to vary the magnitude of said component and determine the value of torque transmitted between the-members-at which the relative movement occursbe-t-weensaid elements.

3. 'A torque applying tool comprising a driven member adapted to"beiconnectcdto aworkpiece a driving member having one endpivotally'engaging said driven member, a yieldable coupling interposedbetween-said members, said couplinginclud-ing first adjustable means for predetermining, in accordance -with the torque desired'to be transmitted by'said tool, the force at which said coupling will yield, and-second adjustable means for predetermining, in accordance with the .length of the driven memberpthe. valueof force at which said coupling will yield, each of said means exerting constant influence on, the coupling yield force throughout adjustment of the other of said means.

4. -An attachment for a torque applying toolcompnising adriven member defining an axis and .adapted to be connected to said 1001, a driving-member coaxial with said driven member and having-one end pivotally engaging said 'driven member, a force-resolving releasable coupling interposed between the-other end of s'aid driving member and saiddriven member,-settable force transmitting means on one member for predetermining, in accordance with the value of torque to be transmitted, the relative-value of component forces which said coupling will produce, and settable reaction means on said driven member for predetermining, in accordance with a dimension of said tool, the reactionforce opposing one of said components at which said couplingwill release, the reaction meansand the force transmitting means beingeffectively-fixed relative to each other during setting thereof whereby the said component forces and reaction force may be established independently to, determine the torque lobe-transmitted.

5. A torque tool for transmitting a predetermined value of torque c omprising a driven member adapted to be connected to a workpiece, a driving member connected adjacent one-end with said driven member, releasable coupling means interposed between the other end of said driving member and said driven member including first and second force transmitting elements, the first of said elements being guidably supported by one of said members and presenting a variable slope surface for engagement by the second of said elements, the second of said elements being supported by the other of said members and being relatively movable between first and second positions, said second element having a portion engaging said variable slope surface at a point in said first position and a portion engaging said variable slope surface at a different point in said second position, and yieldable means urging said elements into engagement with the same force in both said first and second positions of the second of said elements.

6. A torque tool comprising a driving member and a driven member interconnected by a releasable coupling including a first force transmitting element having a variable slope surface and supported by one of said members, a second force transmitting element engageable with said first element and supported by the other of said members, yieldable means urging said elements into engagement, one of said elements being movably mounted for positional adjustment to permit the selection of the slope of said surface at which said elements are engaged, and a reaction portion on one of said elements fixed relative to and engaging said yieldable means during said adjustment whereby the force exerted by the yieldable means is independent of said adjustment.

7. In a torque applying tool of the type including a :10. 1 driving. member and a; driven member interconnected y a yieldable coupling, the improvement in; said ,coiipling comprising -.a first force transmitting element supported by: .one of said members i and; having a. variable; slope surface, .a second force: transmitting elementsupportediby the other. of said-members forengagement-witha selectable -.portion-of the variable slopesurface of said 'first element, ands-mutually independentmeans forpredeter mining the value of force at which saidcoupling will yield including elastic'force exerting means adjacent oneiof said elements urging said elements into engagement,; and including: rotatable adjusting means on the other jot-said elements for relatively displacing said elements, topermit selection of the portion of thevariableslope surface at which engagement iseffective.

8, A torque applying tool comprisinga driven ,member defining an axis .and' adapted tobe connected to a workpiece, a driving; member including means for wi lsmitting a: force. and being coaxial with said, driven member, means rotatably connecting. said .driven member-to said driving member .to prevent transverse movement thereof, -a releasable coupling interposed between the driving member and driven member, said couplingineluding .a'first forcetransmitting element andasecond force transmitting element, the first element having a variableslope surfaceqand being supported by one of'said members. for translational'movement, the second element 'beingssupported by the.- ot-hen ofsaid members and-engag ing said surface, adjustable elastic means urging said-elements into engagement, and independently adjustable movable means on the second element for varying-the point of engagementof said first and second elements in accordance with the value of torque to be applied.

9. A torque tool comprising aqdriving member-and a driven member interconnectedby a releasable coup-ling, said coupling including first and second force transmitting elements=being relatively movable in a direction away from eachother and resisting, means urging the elements toward engagement, the'first element hav ing a surface with a variable slope which increases with displacement in saiddirection and being supported on one of said members, =the second'element'being supported on the other of said members whereby an angularly directed force having-a component in said direction is transmitted between ,the'elements, .means for adjusting the resisting means to vary the magnitude of resistance, and means for adjusting the relative position of the elements to vary the magnitude of said component and thereby determine the value of torque at which relative movement is produced between the elements, the rate of change of said component due to said slope exceeding the rate of change of said resistance due to said movement.

10. An attachment for a torque applying tool comprising a driven member defining an axial bore and adapted to be connected to a lever of said tool, an exterior driving member coaxial with and having one end pivotally engaging said driven member, a releasable coupling between the other end of said driving member and said driven member, said coupling including a first element removably supported on said driving member and having a body portion defining plural circular openings of different diameters, said first element being supported with one of said openings in alignment with the said bore, a second element slidably supported in the bore of said driven member and having a variable slope surface engaging the periphery of one of said openings, and a spring in said bore urging said elements together, said body portion being positionable to selectably align said openings with said bore, each said periphery engaging a point of different slope on said second element to maintain the same position thereof for each selected opening whereby the torque transmitted is determined without disturbing the force of said spring.

11. A torque applying tool comprising a driven member adapted to be connected to a workpiece at one end,

11 a driving member connectedfto said driven member for pivotalmotion about asingle transverse: axis, a releasable coupling comprising a first force transmitting element slidably supported within a recess in one of said members and having a variable slope surface, a second force transmitting element supported on the other of said members in opposed-relation to said surface of .said first element, resilient means in said recess urging .said elements into engagement, said second element including a rotatable shaft portion extending at a right angle to said single transverse axis and having a shouldered portion of varying radius engaging said surface, whereby the release force of said coupling is a function of the rotative position of said shaft. 1 l2.---A coupling for interconnecting a driving member and a driven member providingan adjustable coupling release force comprising a first element having a shaft portion journalled in one of said members for rotation about the shaft axis and a detent portion defining a groove extending circumferentially of said shaft portion, said groove being circular in cross section, the root of said groove being concentric with said shaft axis and the peripheral edge of said groove being eccentric with said shaft axis, a second element slidably supported by the other of said members for motion toward and away from said first element and having a hemispherical surface in mating alignment with said groove, a spring urging said elements into engagement whereby the second element is at a fixed distance from said shaft axis for all rotative positions of said shaft and the release force of said coupling for all of said rotative positions is independent of the spring rate.

13. A coupling as defined in claim 12 wherein the peripheral edge of said groove is tangent at a single point to the root of said groove and the maximum depth of said groove is equal to the radius of curvature of said hemispherical surface whereby said coupling will release at substantially zero force value in one position and is effectively non-releasable in another position.

14. An attachment for a torque applying tool comprising a driven member adapted to be connected at one end to a lever of said tool, said member defining an axially extending recess at the other end, a driving member adapted to receive a manually exerted force pivotally connected adjacent one of its ends to said driven member, a releasable coupling interposed between the arsasrs other end of said driven member and said driving member including: a ball slidably supported in said recess, a detent part having a shaft rotatably journalled in said driving member, said detent part defining a groove circu lar in cross section and extending circumferentially of said shaft and having a depth varying with circumferential position, a spring in said recess urging said ball into engagement with the wall of said groove, means for ad justing the force exerted by said spring, and means for rotatably positioning said shaft.

15. A torque applying tool comprising a driven member adapted to be connected to a workpiece at one end, said driven member defining an axially extending recess at the other end, an exterior driving member connected to said driven member for pivotal motion about a single transverse axis, a releasable coupling interposed between the ,other end of said driven member and said driving member including; a first spherical force transmitting ele ment slidably supported in said recess by said driven member, a second force transmitting element having a shaft rotatably journalled in said driving member for rotation about an axis perpendicular to said single axis, said second element defining a groove circular in cross section and extending circumferentially of said shaft, a spring in said recess urging said first element into said groove, the root of said groove being coaxial with said shaft and the peripheral edge of said groove being eccentric of said shaft, whereby the position of said first element and the deflection of said spring is independent of the rotative position of said shaft, means for adjusting the force of said spring in accordance with the effective lever arm of said tool, and means for rotatively positioning said shaft in accordance with the torque desired to be applied by said tool.

References Cited in the file of this patent UNITED STATES PATENTS 1,847,640 Cairncross et a1 Mar. 1, 1932 2,300,652 Cooney Nov. 3, 1942 2,365,486 Morris Dec. 19, 1944 2,400,205 Livermont May 14, 1946 2,686,446 Livermont Aug. 17, 1954 2,732,747 Livermont Jan. 31, 1956 FOREIGN PATENTS 3 717,570 Germany Feb. 17, 1942 

